Term
| adaptation, or adaptive trait |
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Definition
| any heritable trait that enables an individual organism to survive through natural selection and to reproduce more than other individuals under prevailing environmental conditions. |
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| Throughout most of history, species have disappeared at a low rate, called background extinction. |
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| biological diversity, or biodiversity |
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Definition
| the variety of the earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life. |
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| the process whereby earth’s life changes over time through changes in the genes of populations. |
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Term
| differential reproduction |
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Definition
| For natural selection to occur, a trait must be heritable, meaning that it can be passed from one generation to another. The trait must also lead to differential reproduction, which enables individuals with the trait to leave more offspring than other members of the population leave. |
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| Scientists describe the role that a species plays in its ecosystem as its ecological niche, or simply niche (pronounced “nitch”). It is a species’ way of life in a community and includes everything that affects its survival and reproduction, such as how much water and sunlight it needs, how much space it requires, and the temperatures it can tolerate. |
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| Species that are found in only one area are called endemic species and are especially vulnerable to extinction. |
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| Another process affecting the number and types of species on the earth is extinction, in which an entire species ceases to exist. |
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| Most of what we know of the earth’s life history comes from fossils: mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items found in rocks. |
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| Another important type of species in some ecosystems is a foundation species, which plays a major role in shaping communities by creating and enhancing their habitats in ways that benefit other species. |
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| Generalist species have broad niches. They can live in many different places, eat a variety of foods, and often tolerate a wide range of environmental conditions. |
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| occurs when different groups of the same population of a species become physically isolated from one another for long periods. |
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| Species that provide early warnings of damage to a community or an ecosystem are called indicator species. |
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| A keystone is the wedge-shaped stone placed at the top of a stone archway. Remove this stone and the arch collapses. In some communities and ecosystems, ecologists hypothesize that certain species play a similar role. Keystone species have a large effect on the types and abundances of other species in an ecosystem. |
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| is a significant rise in extinction rates above the background level. |
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| The first step in this process is the development of genetic variability in a population.This genetic variety occurs through mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring. |
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| are those species that normally live and thrive in a particular ecosystem. |
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| Darwin and Wallace concluded that these survival traits would become more prevalent in future populations of the species through a process called natural selection, which occurs when some individuals of a population have genetically based traits that enhance their ability to survive and produce offspring with the same traits. |
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| Other species that migrate into or are deliberately or accidentally introduced into an ecosystem are called nonnative species, also referred to as invasive, alien, or exotic species. |
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| mutation and change by natural selection operate independently in the gene pools of geographically isolated populations. |
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| In contrast, specialist species occupy narrow niches. They may be able to live in only one type of habitat, use one or a few types of food, or tolerate a narrow range of climatic and other environmental conditions. |
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| Under certain circumstances, natural selection can lead to an entirely new species. In this process, called speciation, two species arise from one. |
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Definition
| An important characteristic of a community and the ecosystem to which it belongs is its species diversity the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species (species evenness). |
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Term
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Definition
| An important characteristic of a community and the ecosystem to which it belongs is its species diversity: the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species (species evenness). |
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Term
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Definition
| An important characteristic of a community and the ecosystem to which it belongs is its species diversity: the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species (species evenness). |
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